###Live Caption:An approximately 90-foot long gash stretches down the Cosco Busan's hull as it rests at anchor on Tuesday, Nov. 13, 2007, in the San Francisco Bay, Calif. The vessel struck the Bay Bridge last Wednesday spilling about 58,000 gallons of oil into the bay. BY NOAH BERGER/SPECIAL TO THE CHRONICLE. EDITOR: DO NOT RELEASE TO ANY WIRE OR OTHER NEWSPAPER. CHRONICLE USE ONLY.###Caption History:busan_nb4
An approximately 90-foot long gash stretches down the Cosco Busan's hull as it rests at anchor on Tuesday, Nov. 13, 2007, in the San Francisco Bay, Calif. The vessel struck the Bay Bridge last Wednesday spilling about 58,000 gallons of oil into the bay.
BY NOAH BERGER/SPECIAL TO THE CHRONICLE.
EDITOR: DO NOT RELEASE TO ANY WIRE OR OTHER NEWSPAPER. CHRONICLE USE ONLY.###Notes:###Special Instructions: less

###Live Caption:An approximately 90-foot long gash stretches down the Cosco Busan's hull as it rests at anchor on Tuesday, Nov. 13, 2007, in the San Francisco Bay, Calif. The vessel struck the Bay Bridge last ... more

Photo: Noah Berger

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The Cosco Busan heads out under the Golden Gate Bridge.
The Cosco Busan sails out of San Francisco Bay today after it hit the Bay Bridge on Nov 7th spilling 58,000 gallons of bunker oil into the bay.
SPILL_SHIP_0090_KR.jpg
Kurt Rogers / The Chronicle Photo taken on 12/20/07, in San Francisco, CA, USA less

The Cosco Busan heads out under the Golden Gate Bridge.
The Cosco Busan sails out of San Francisco Bay today after it hit the Bay Bridge on Nov 7th spilling 58,000 gallons of bunker oil into the bay. ... more

Photo: Kurt Rogers

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Cosco Busan set sail today from Anchorage 9 off Hunters Point, heading out the Golden Gate and points west. Frederic Larson / The Chronicle
Photo taken on 12/21/07, in San Francisco, CA, USACosco Busan set sail today from Anchorage 9 off Hunters Point, heading out the Golden Gate and points west. Frederic Larson / The Chronicle
Photo taken on 12/21/07, in San Francisco, CA, USA less

Cosco Busan set sail today from Anchorage 9 off Hunters Point, heading out the Golden Gate and points west. Frederic Larson / The Chronicle
Photo taken on 12/21/07, in San Francisco, CA, USACosco Busan set ... more

Photo: Frederic Larson

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Cosco Busan faulted for sailing in heavy fog

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The fog was so heavy the morning the Cosco Busan struck the Bay Bridge that at least four other large vessels decided to wait until it cleared, the Coast Guard said Thursday.

A preliminary assessment by the Coast Guard of the causes of the crash concludes that the decision of those in charge of the container ship to set sail in dense fog played a key role in the Nov. 7 accident, which spilled 53,000 gallons of fuel oil into the bay, fouling miles of Bay Area and ocean shoreline and killing thousands of birds.

"Pretty clearly, this vessel got under way in fog (when there) was less than a quarter-mile of visibility," Rear Adm. Craig Bone, the service's top commander in California, said at a briefing in Washington.

"There were other deep-draft vessels also scheduled to depart that day where the vessel master, crew and other individuals involved in that decision deemed it prudent to not get under way until visibility improved," Bone said.

To prevent a repeat of the Cosco Busan crash, the Coast Guard has restricted vessels weighing more than 1,600 gross tons - such as tankers, large cargo vessels and cruise ships - from sailing on the bay when visibility is less than half a mile.

The rules will apply to nine areas - including those near the Bay Bridge, the San Mateo Bridge and the Richmond-San Rafael Bridge - where navigation could be particularly dangerous in the fog.

Bone said investigators from the Coast Guard, the National Transportation Safety Board and other agencies have found no evidence that any mechanical or systems failures on the Cosco Busan contributed to the crash.

"Human error is the dominant factor involved," he said.

The Coast Guard showed video from the agency's vessel traffic service cameras on Yerba Buena Island taken the morning of the accident. The cameras, one pointing toward Oakland and the other toward San Francisco, showed a thick wall of fog.

"There was discussion by individuals (on several vessels around the bay) to the fact that they couldn't even see the bow of the ship," Bone said.

The Coast Guard said the decision to sail would have been made by the master of the Cosco Busan and the ship's pilot, Capt. John Cota, who has pleaded not guilty to misdemeanor violations of the federal Clean Water Act and Migratory Bird Treaty Act in connection with the spill.

Bone said representatives of a ship's owner are sometimes involved in sailing decisions, although it's not yet clear whether the Cosco Busan's owner was consulted before the 901-foot ship left port.

The Coast Guard report also suggests that Cota and the ship's master, Capt. Mao Cai Sun, made other errors as they steered the ship out of the Port of Oakland and toward the bridge.

Investigators are looking at the speed of the vessel, which struck the second tower west of Yerba Buena at about 10 knots, or 11.5 mph, Coast Guard officials said. The agency's charts show the vessel took a very wide turn heading into the bridge, despite receiving guidance from a Coast Guard vessel traffic service operator indicating that the ship appeared to be off course.

"If you're going to get under way in conditions like this, the rules of the road basically give guidance on additional caution and prudence" regarding speed and other navigational issues, Bone said.

The Coast Guard also made public an audiotape of conversations between the vessel traffic service and Cota before the ship hit the bridge. The tape confirms that an operator questioned Cota as he appeared to be heading toward the span, saying, "What are your intentions?"

"Roger, then you still intend the Delta-Echo span?" the operator said, seeking to confirm that Cota was still heading between the two towers closest to Yerba Buena on the west side of the island.

The operator did not give specific advice on where Cota or the ship's master should steer. Moments later, Cota came back on the radio to alert the operator the vessel had struck the bridge. "Traffic, we just touched the Delta span," said the 27-year veteran pilot.

Cota's attorney, Jeff Bornstein, could not be reached for comment Thursday.

-- That foggy day: The Coast Guard shot video the morning of the Cosco Busan crash from two cameras on Yerba Buena Island, one pointing toward Oakland and the other toward San Francisco. The video can be viewed at: sfgate.com/ZCVM and sfgate.com/ZCVN.

New rules for fog

To prevent a repeat of the Cosco Busan accident, the Coast Guard now bars ships weighing more than 1,600 gross tons from sailing when visibility is less than half a mile in nine areas of the bay:

-- Redwood Creek, near the Port of Redwood City

-- San Mateo Bridge

-- Oakland Bar Channel, near the Bay Bridge and Yerba Buena Island

-- Islais Creek Channel off San Francisco

-- Richmond Inner Harbor

-- Richmond-San Rafael Bridge, East Span

-- Union Pacific Bridge, in the Carquinez Strait

-- New York Slough, at the mouth of the Sacramento-San Joaquin River Delta.